Listeria

Question 1

what is the paradigm of Listeria monocytogenes

Answer 1

invasive, pore-forming toxin

Question 2

what does listeria monocytogenes cause?

Answer 2

listeriosis

Question 3

gram ? shape ? motile or non motile

Answer 3

gram positive, rod-shaped, motile at 25 degrees, not at 37 degrees, no flagella in the host

Question 4

symptoms

Answer 4

mild flu-like symptoms to infections of CNS like meningitis, encephalitis, and can cause septicaemia

Question 5

listeria in immunocompromised?

Answer 5

can potentially cross the BBB

Question 6

Fatality rate?

Answer 6

20-40%, most common bacterial killer of food borne origin

Question 7

cases of listeriosis are _ but deaths are _

Answer 7

low, high

Question 8

acceptable listeria threshold

Answer 8

zero.

Question 9

what groups of people does listeriosis affect?

Answer 9

YOPI

Question 10

canada case studyi

Answer 10

coleslaw in 1981, source traced back to infected sheep whose maneure was used to fertilise the cabbage, cabbage then stored at low temperature, used to make coleslaw.
34 pregnant women: 9 still birth, 23 infected neonates, 8 deaths, 2 healthy neonates.
7 healthy non-pregnant adults: 2 deaths.

Question 11

what are deaths from listeria in adults linked to usually?

Answer 11

linked to underlying condition which predisposes individual to listeriosis

Question 12

mechanism

Answer 12

can survive acidic stomach, bile resistant, binds to epithelial cells, crosses epithelial barrier, accesses macrophages which drain to lymph nodes, through lymphatics the bacteria will travel within the macrophage to the liver and the spleen. macrophages die, bacteria released, listeria colonises liver and spleen. can enter blood and go to brain, reproductive system, etc.

Question 13

what is needed for systemic listeria infection

Answer 13

colonisation of the liver and spleen

Question 14

pathogenesis: adherence

Answer 14

adhere to epithelial cells, M cells have a role in giving access to listeria to the macrophages for uptake and replication within the macrophages.
mainly mediated by internalin A and internalin B.

Question 15

what are internalin A and internalin B?

Answer 15

these are adhesins which are on the surface of the bacteria which aid the adhesion of the bacteria to the host cells, induce phagocytosis into the epithelial cells, transverse cell and exit on basolateral side where they can interact with macrophages, be phagocytosed and brought to secondary lymphoid organs and then only liver and spleen, macrophages broken down, listeria released and can cause systemic effects.

Question 16

what does internalin A adere to?

Answer 16

e-cadherin, protein found in epithelial cells, associated with tight junctions, binds eukaryotic cells together.

Question 17

why is mouse a poor model?

Answer 17

because it has a different e-cadherin

Question 18

which internalin is most helpful for crossing barriers?

Answer 18

internalin A is most involved in crossing placental barrier, BBB and intestinal barrier

Question 19

main role of internalin B

Answer 19

mostly involved in the ubiquitous spread of the bacterium into liver, spleen, etc.

Question 20

what is rearranged to endocytose listeria bound to e-cadherin?

Answer 20

actin

Question 21

what does internalin B bind to?

Answer 21

met

Question 22

internalin A binds to _ and promotes _ in the _ tract

Answer 22

internalin A binds to e-cadherin and promotes uptake in the gastrointestinal tract.

Question 23

internalin B binds to _ and promotes _ _.

Answer 23

internalin B binds to Met and promotes systemic spread.

Question 24

why is mouse a poor model?

Answer 24

internalin A on the bacteria does not bind to mouse e-cadherin as well as in human, is representative of systemic spread as internalin B binds to mouse met

Question 25

what is LLO?

Answer 25

a pore-forming toxin called Listeriolysin ruptures phagosome containing bacteria. inserts into phagosomal membrane and releases bacteria into cytoplasm

Question 26

how does listeria move when it is in the host

Answer 26

no flagella but polymerise actin to allow movement

Question 27

what does ActA

Answer 27

assembles at one pole of cell, stimulates polymerisation of actin and pushes it from one host cell to a neighboring host cell.

Question 28

after spread to neighboring cell, what kind of vacuole is the bacterium found in?

Answer 28

a double-membrane vacuole.

Question 29

four virulence factors for listeria

Answer 29

Act A, internalins, listeriolysin and leichtinases

Question 30

LLO

Answer 30

only active at a low pH, does not destroy cell membrane

Question 31

pH of phagosome

Answer 31

acidic

Question 32

at what pH is LLO active at?

Answer 32

low pH

Question 33

is the LLO active outside of the phagosome?

Answer 33

no because it would cause cell lysis and not give the bacteria enough time to grow.

Question 34

are LLO mutants more or less virulent?

Answer 34

less virulent

Question 35

LLO structure

Answer 35

pore-forming toxin, scorpion tail shape, active (pore-forming component) poised to strike a membrane and form a pore. cholesterol binding part for cell membranes of eukaryotic cells.

Question 36

extracellular roles for LLO

Answer 36

some evidence that not all LLO is fully inactivated by the proteolysis in the cell. what is left isn’t enough to kill the cell but is involved in virulence
can insert in host cell membrane, ion flux of calcium and potassium, mitochondrial fragmentation, modify histones

Question 37

what virulence genes are not located in the PrfA controlled operon?

Answer 37

internalin A and internalin B